#include<stdio.h>
#define N 350
int n,m,k,c[N][N],f[N][N],i,s,d,p[N],t,l,h[N],r[N],j,g[N][N],a[N],o[N][N],b[N],q,w;
long e;
int main()
{freopen("fmcm.in","r",stdin),freopen("fmcm.out","w",stdout);
scanf("%d%d%d%d",&n,&m,&s,&d);
s--,d--;
while(m--)
          scanf("%d%d%d%d",&i,&j,&l,&k),i--,j--,g[i][a[i]++]=j,g[j][a[j]++]=i,o[i][j]=k,o[j][i]=-k,c[i][j]=l;
while(1)      
          {for(i=0;i<n;i++)
                   b[i]=10001,r[i]=-1;
          b[h[0]=s]=0,m=10001,l=1,p[d]=-1;
          while(l)
                   {r[i=h[0]]=-1,r[h[0]=h[--l]]=j=k=0;
                   while(k<l)
                          {if(k+1<l&&b[h[k+1]]<b[h[k]])
                                 k++;
                          if(b[h[j]]<=b[h[k]])
                                 break;
                          t=h[k],q=h[j],r[h[j]=t]=j,r[h[k]=q]=j=k,k<<=1;}
                   for(k=0;k<a[i];k++)
                   if(b[w=g[i][k]]>b[i]+o[i][w]&&c[i][w]>f[i][w])
                          {b[w]=b[i]+o[i][w],p[w]=i,j=r[w];
                          if(j<0)
                                 j=r[w]=l,h[l++]=w;
                          q=h[j];
                          for(t=j>>1;t&&b[h[t]]>b[q];j=t,t>>=1)
                                 h[j]=h[t],r[h[j]]=j;
                          h[j]=q,r[q]=j;}}
          if(p[d]<0)
                   break;
          for(l=d;l!=s;l=p[l])
          if(m>(t=c[p[l]][l]-f[p[l]][l]))
                   m=t;
          for(l=d;l!=s;l=p[l])
                   f[p[l]][l]+=m,f[l][p[l]]-=m;
          e+=b[d]*m;}
printf("%ld",e);
return 0;}